1. Field
The present disclosure relates to a differential pressure water electrolysis system.
2. Description of the Related Art
Typically, hydrogen gas is used as a fuel gas used to perform a power generation reaction in a fuel cell. The above hydrogen is produced by a water electrolyzer, for example. The water electrolyzer uses a solid polymer electrolyte membrane (an ion-exchange membrane) for generating hydrogen (and oxygen) through electrolysis of water.
An electrode catalyst layer is provided on both surfaces of the solid polymer electrolyte membrane such that an electrolyte membrane-electrode structure is configured, and a current collector is disposed on both sides of the electrolyte membrane-electrode structure such that a water electrolysis cell is configured.
In a water electrolyzer in which a plurality of water electrolysis cells are stacked, voltage is applied to both ends in a stacking direction and water is supplied to an anode current collector. Accordingly, water is electrolyzed and hydrogen ions (protons) are generated on the anode side of the electrolyte membrane-electrode structure, the hydrogen ions permeate the solid polymer electrolyte membrane and is transferred to the cathode side, and the hydrogen ions are combined with the electrons in a cathode current collector such that hydrogen is produced. Meanwhile, on the anode side, oxygen that has been generated together with hydrogen is discharged from the water electrolyzer together with surplus water.
As the water electrolyzer, a differential pressure water electrolysis system that, while producing oxygen on the anode side, produces, on the cathode side, hydrogen that has a higher pressure with respect to the pressure of the oxygen by electrolyzing water is employed. Specifically, current collectors are provided on both sides of the solid polymer electrolyte membrane and separators are stacked on the current collectors and, further, a water flow passage that supplies water is formed between one of the current collectors and one of the separators. Furthermore, a hydrogen flow passage that obtains hydrogen generated through electrolysis of water and that has a high-pressure that is higher than the normal pressure is formed between the other current collector and the other separator.
For example, the water electrolyzer disclosed in Japanese Unexamined Patent Application Publication No. 2011-127209 includes a unit cell in which an anode side separator and a cathode side separator holds an electrolyte membrane-electrode structure in between. The water electrolyzer includes a plurality of unit cells stacked on each other. In the water electrolyzer, a water inlet manifold for supplying water for electrolysis to the water flow passages of the unit cells extend in the stacking direction and a water outlet manifold for discharging the water after electrolysis from the water flow passages extend in the stacking direction.
Accordingly, a plurality of inlet connection flow passages that communicate the water inlet manifold and the water flow passage, and a plurality of outlet connection flow passage that communicate with the discharge manifold are provided in each anode side separator.